This important fact might be illustrated by an immense number of examples. It is evidently, therefore, not the number of actually existing germs which indicates the number of individuals which afterwards come into life and maintain themselves in life; but rather the case is this, that the number of adult individuals is limited by other circumstances, especially by the relations in which the organism stands to its organic and inorganic surroundings. Every organism, from the commencement of its existence, struggles with a number of hostile influences: it struggles against animals which feed on it, and to which it is the natural food, against animals of prey and parasites; it struggles against inorganic influences of the most varied kinds, against temperature, weather, and other circumstances; but it also struggles (and this is much the most important!), above all, against organisms most like and akin to itself. Every individual, of every animal and vegetable species, is engaged in the fiercest competition with every other individual of the same species which lives in the same place with it. In the economy of nature the means of subsistence are nowhere scattered in abundance, but are very limited, and far from sufficient for the number of organisms which might develop from the germs produced. Therefore the young individuals of most species of animals and vegetables must have hard work in obtaining the means of subsistence; this necessarily causes a competition among them in order to obtain the indispensable supplies of life.
This great competition for the necessaries of life goes on everywhere and at all times, among human beings and animals as well as among plants; in the case of the latter this circumstance, at first sight, is not so clearly apparent. If we examine a field which is richly sown with wheat, we can see that of the numerous young plants (perhaps some thousands) which shoot up on a limited space, only a very small proportion preserve themselves in life. A competition takes place for the space of ground which each plant requires for fixing its root, a competition for sunlight and moisture. And in the same manner we find that, among all animal species, all the individuals of one and the same species compete with one another to obtain these indispensable means of life, or the conditions of existence in the wide sense of the word. They are equally indispensable to all, but really fall to the lot of only a few--"Many are called, but few are chosen." The fact of the great competition is quite universal. You need only to cast a glance at human society, where this competition exists everywhere, and in all the different branches of human activity. Here, too, a struggle is brought about by the free competition of the different labourers of one and the same class. Here too, as everywhere, this competition benefits the thing, or the work, which is the object of competition. The greater and more general the competition, the more quickly improvements and inventions are made in the branch of labour, and the higher is the grade of perfection of the labourers themselves.